Slider pad for roller finger follower

ABSTRACT

A roller finger follower is provided having a housing and two separate outer arms mounted at one end to a pivot axle that extends through the housing. A roller is mounted in the housing The outer arms extend longitudinally along sides of the housing and include high lift cam contact surfaces. The outer arms having an outer arm body and separately formed longitudinal body, retained on the outer arm body, the longitudinal body including the cam contact surface. The longitudinal body is formed of a high durability material or coated with a suitable coating, the outer arm body formed of a lower grade, lower cost material.

TECHNICAL FIELD

Example aspects described herein relate to roller finger followers that are used in overhead cam type internal combustion engines and, more particularly, to switchable roller finger followers.

BACKGROUND

Switchable roller finger followers are known. See, for example, U.S. Pat. No. 7,174,869. Such finger followers have an outer lever pivotably mounted outside an inner lever and a roller rotatably mounted on a transverse axle in a slot in the inner lever. The top surface of the outer lever acts as a contact surface for a high lift cam and the top surface of the roller acts as a contact surface for a low lift cam. A coupling element is mounted at one end of the finger and oil from an oil source is used to activate the coupling element. When the coupling element is activated, it locks the outer lever to the inner lever and requires the follower to follow the high lift cam and transfer the lift to the valve stem of an associated intake or exhaust valve. When the coupling element is deactivated, the outer lever is free to pivot relative to the inner lever and, under the aid of a spring, the outer lever pivots freely in conjunction with the high lift cam while the motion of the low lift cam is transferred by the inner lever to the valve stem. This movement by the outer lever is conventionally referred to as the lost motion stroke.

Conventionally, the outer lever is a unitary structure such that the coupling element need only operate on one part of the outer lever. Typically, the coupling device operates on a yoke portion of the outer lever, the yoke portion being transverse to the longitudinal axis of the finger follower. Conventionally, the roller axle is staked to the inner lever to maintain its lateral position relative to the inner lever. U.S. Pat. No. 7,909,007 discloses a roller finger follower of this type. This provides a lost motion spring to maintain contact between the cam follower and the cam.

US2011/0197843 discloses the inventor's prior switchable roller finger follower in which the outer arm is formed by two separate outer arms that can move independently from one another and are connected to a common coupling element. However, the outer arms have a fairly complex configuration and associated cost. In order to produce the separate arms, and associated sliding pad contacts, to withstand valvetrain, and more specifically, cam lobe loads, particular materials, such as bearing grade steel, or specific materials along with special coatings, such as diamond-like carbon coatings, are used. US2011/0197843 is incorporated herein by reference as if fully set forth.

SUMMARY

Briefly stated, a roller finger follower is provided having a housing and two separate outer arms mounted at one end to a pivot axle that extends through an opening in a first end of the housing. A roller is rotatably mounted on a transverse axle in a slot in the housing. The outer arms extend longitudinally along sides of the housing towards the other end of the inner lever and include high lift cam contact surfaces located adjacent to the roller. Each of the outer arms are formed of at least two pieces; an outer arm body with a longitudinal depression at an upper periphery; and a longitudinal body of a size and shape to fit into the depression, and retained to the outer arm body by any known means, such as laser welding or press fitting. The outer arm body can be provided with a slot adjacent the depression to mate with a radially extending retention feature, extending from a lower periphery of the longitudinal body. The longitudinal body can be formed of high durability material, such as bearing steel or coated with a suitable coating, such as amorphous hydrocarbon. The outer arm body can be formed of a lower grade and lower cost material, such as tool steel.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing Summary and the following detailed description will be better understood when read in conjunction with the appended drawings, which illustrate a preferred embodiment of the invention. In the drawings:

FIG. 1 is a perspective view of a switchable finger follower according to one example embodiment;

FIG. 2 is a side view of an outer arm for a switchable roller finger follower, with slider pad insert, according to one example embodiment;

FIG. 3 is a perspective view of the outer arm with slider pad insert of FIG. 2;

FIG. 4 is a perspective view of the slider pad insert of FIG. 2;

FIG. 5 is a perspective view of the outer arm, without the slider pad insert, of FIG. 2.

DETAILED DESCRIPTION

Certain terminology is used in the following description for convenience only and is not limiting. The words “front,” “rear,” “upper” and “lower” designate directions in the drawings to which reference is made. The words “inwardly” and “outwardly” refer to directions toward and away from the parts referenced in the drawings. A reference to a list of items that are cited as “at least one of a, b, or c” (where a, b, and c represent the items being listed) means any single one of the items a, b, or c, or combinations thereof. The terminology includes the words specifically noted above, derivatives thereof and words of similar import.

FIG. 1 shows a switchable finger follower 100 according to one example embodiment. Finger Follower 100 comprises main housing or primary lever 101, low lift cam follower 102, secondary lever or outer arms 1, assembled onto pivot axle 112 and retained onto axle 112 by retention clips 113, locking pin 103, and lost motion springs 114, 115 assembled onto spring pin 116. Secondary lever or outer arms 1 are selectively lockable and unlockable by longitudinal movement of locking pin 103, orthogonal to pivot axis T of outer arms 1 and actuated by introduction of pressurized hydraulic fluid or any other known means. In another embodiment, a single secondary lever can replace outer arms 1 without impacting the scope of the present disclosure. High lift cam lobes (not shown) of a camshaft (not shown) contact upper contact surfaces 120 of arms 1. Housing 101 includes wall 130, wall 131 and interior space 132 at least partially formed by walls 130 and 131. Low lift cam follower or roller 102 is inserted into space 132, and retained in position by a transverse axle (not shown) extending substantially through walls 130, 131 and cam follower 102.

When locking pin 103 is in locked mode, namely, moved longitudinally inward, toward arms 1 and contacts lower contact arm 122, 123 of outer arms 1 the contact of high lift cam lobes with the respective upper contact surfaces 120 pivots finger follower 100 about an associated pivot element (not shown) at end B, and causes a high lift of an associated valve (not shown) at end A. When locking pin 103 is in unlocked mode, namely when moved longitudinally outward, away from arms 1, the contact of high lift came lobes with upper contact surfaces 120 causes lost motion movement of outer arms 1 against spring arms 117, 118 of springs 115, 114, respectively, in contact with outer arms 1 at lost motion guides 125, 126, respectively.

FIG. 2 is a side view of outer arm 1 for a switchable roller finger follower, including slider pad insert 2 and outer arm body 3, according to one example embodiment. FIG. 3 is a perspective view of outer arm 1 of FIG. 2. FIGS. 4 and 5 are perspective views of slider pad insert 2 and outer arm body 3 of FIG. 2, respectively. The following description should be viewed in light of FIGS. 2 through 5. Outer arm 1 comprises two assembled pieces; slider pad insert 2, made of a hard material, or a material suitable for coating, then coated, in order to withstand contact stresses associated with contact with cam lobes during operation; and outer arm body 3, made of standard tool steel or other suitable material. In this embodiment, arm 1 would be one of two arms, such as that shown in follower 100. It will be understood by one skilled in the art, that, although separate outer arms are described herein, slider pad inserts may be used in finger follower arrangements similar to that described in U.S. Pat. Nos. 7,174,869 and 7,909,007.

In this example embodiment, slider pad insert 2 is comprised of an upper curved longitudinal piece 5, with an upper contact surface 6 of a length and area required to accept contact with an associated cam lobe (not shown) for any particular application, such that the cam lobe does not have substantial contact with the upper surface of outer arm body 3 during operation, a lower retention piece 7 and a neck portion or post 8, radially connecting longitudinal piece 5 with retention piece 7. Retention piece 7 is shown as a rectangular parallelepiped, substantially shorter in length than longitudinal piece 5 and longer than neck portion or post 8. In an example embodiment, retention piece 7 is ⅓ the length of longitudinal piece 5, though one skilled in the art will understand that retention piece 7 can be longer. When slider pad insert 2 is inserted into outer arm body 3, more specifically into insert slot 10, lower radial surface 20 of radial retention tab 11 contacts upper radial surface 13 of retention piece 7, and against side surface 14 of neck 8, and lower surface 21 of tab 12 contacts upper radial contact surface 15 of retention piece 7 and side surface 16 of neck 8. In this manner slider pad insert 2 is retained in a radial direction and in a direction orthogonal to pivot axis P of arm 1. Slider insert pad 2 can be retained in a direction parallel to pivot axis P, by at least one of press fitting, staking, laser welding or any other suitable fixation means known in the art. It will be understood by one skilled in the art that retention of insert 2 within body 3 does not have to take the particular form described, but can take any variety of suitable forms, including, but, not limited to a triangular retention piece 7, multiple retention pieces, retention pieces at longitudinal ends of upper longitudinal piece 5, or, no retention piece, instead only using one of the means described, namely, staking, laser welding and the like.

Outer arm body 3 can take a variety of forms, however, in the embodiment described, in addition to insert slot 10, body 3 comprises pivot hole 31, to receive pivot pin (not shown) of an associated finger follower assembly, lost motion spring arm guide 32 and depression 30, of a length and depth such that upper contact 6 of insert 2 is coincident with upper radial periphery or surface 35 at both longitudinal ends of body 3.

As previously described, insert 2 is preferably made of a material suitable to withstand required contact pressures, such as one of bearing grade steel, for example SAE 52100, or a material suitable to accept a coating, for example X210CrW12 steel, coated on an outer surface with a suitable coating, such as an amorphous hydrocarbon. The amorphous hydrocarbon includes metal free amorphous hydrocarbon. The amorphous hydrocarbon also includes metal-free amorphous hydrocarbon with sp² and sp³ hybridized carbon. Further detail regarding a layer of amorphous hydrocarbon, metal-free amorphous hydrocarbon, or metal-free amorphous hydrocarbon with sp² and sp^(a) hybridized carbon is provided in commonly-owned U.S. Pat. Nos. 7,363,894 and 8,161,925, which patents are incorporated in their entirety herein. Arm body 3 can be made of any suitable material, preferably low cost material, for example standard tool steel.

While the preferred embodiment of the invention has been described in detail, those skilled in the art will recognize that other changes could be made to a switchable roller finger follower without departing from the scope of the present invention. Other types of arm or slider pad arrangements could be provided and the specific configuration of the insert relative to the roller finger follower and arm or wall could be varied without departing from the scope of the present invention. Accordingly, the scope of the invention should not be limited by the preferred embodiments discussed above and instead should be defined by the claims as noted below. 

What is claimed is:
 1. A roller finger follower for a valve train of an internal combustion engine, comprising: a primary lever having a slot in which a roller is mounted by a transverse axle; a secondary lever that extends along at least one longitudinal side of the primary lever that is mounted for pivoting movement at one end of the primary lever by a pivot axle; the secondary lever including: a body, having a depression along a substantial portion of an upper longitudinal periphery of the lever; a longitudinal body shaped to fit into the depression and retained on the body; the longitudinal body having a high lift cam contact surface located at an upper periphery adjacent to the roller; and a coupling arrangement located between the primary lever and the secondary lever which in a locked position, locks the secondary lever to the primary lever at least in an activation direction of a valve, and in an unlocked position, allows the secondary lever to pivot relative to the primary lever.
 2. The roller finger follower of claim 1, wherein the longitudinal body is made of bearing grade steel, such as SAE
 52100. 3. The roller finger follower of claim 2, wherein the secondary lever body is made of a tool steel.
 4. The roller finger follower of claim 1, wherein the secondary lever body includes a slot at an upper periphery adjacent the depression shaped to accept a retention piece connected to the longitudinal body, the retention piece retaining the longitudinal body to the secondary lever body at least in a radial direction.
 5. The roller finger follower of claim 4, wherein the longitudinal body is additionally retained to the secondary lever body by one of press fitting, staking or laser welding.
 6. The roller finger follower of claim 4, wherein the retention piece is a rectangular prism connected at an upper periphery to the lower periphery of the longitudinal body with a radially extending post.
 7. The roller finger follower of claim 6, wherein the retention piece is substantially shorter in length than the longitudinal body.
 8. The roller finger follower of claim 1, wherein the longitudinal body is made of a coatable material and coated at least at the cam contact surface with amorphous hydrocarbon.
 9. The roller finger follower of claim 8, wherein the amorphous hydrocarbon includes at least one of metal free amorphous hydrocarbon or metal-free amorphous hydrocarbon with sp² and sp³ hybridized carbon.
 10. The roller finger follower of claim 1, wherein the cam contact surface of the longitudinal body is coincident with an upper radial periphery of the secondary lever body, adjacent the depression.
 11. The roller finger follower of claim 1, wherein the secondary lever comprises two separate outer arms.
 12. An outer arm for a three arm switchable roller finger follower for a valve train of an internal combustion engine, comprising: an outer arm body, having a depression along a substantial portion of an upper longitudinal periphery of the arm and a pivot recess to accept a pivot axle; a longitudinal body shaped to fit into the depression and retained on the outer arm body; and the longitudinal body having a high lift cam contact surface located at an upper periphery.
 13. The outer arm of claim 12, wherein the longitudinal body is made of bearing grade steel, such as SAE
 52100. 14. The outer arm of claim 13, wherein the outer arm body is made of a lower grade steel, such as tool steel.
 15. The outer arm of claim 12, wherein the outer arm body includes a slot at an upper periphery adjacent the depression shaped to accept a retention piece connected to the longitudinal body, the retention piece retaining the longitudinal body to the outer arm body at least in a radial direction.
 16. The outer arm of claim 15, wherein the longitudinal body is additionally retained to the outer arm body by one of press fitting, staking or laser welding.
 17. The outer arm of claim 15, wherein the retention piece is a rectangular prism connected at an upper periphery to the lower periphery of the longitudinal body with a radially extending post.
 18. The outer arm of claim 17, wherein the retention piece is substantially shorter in length than the longitudinal body.
 19. The outer arm of claim 12, wherein the longitudinal body is made of a coatable material and coated at least at the cam contact surface with amorphous hydrocarbon.
 20. The outer arm of claim 19, wherein the amorphous hydrocarbon includes at least one of metal free amorphous hydrocarbon or metal-free amorphous hydrocarbon with sp² and sp³ hybridized carbon. 